livecodefandomcom_de-20200214-history
RevQueryDatabase
Selects records in a database according to a SQL query.Syntax: revQueryDatabase(, | }) Examples: revQueryDatabase(2,"SELECT * FROM EmpStats") revQueryDatabase(currentDB,field "Query") revQueryDatabase(the database of me,myQuery,"myVar1","myVar2","myVar3") revQueryDatabase(tConnectionId, tQuery, "tInputDataid", "tInputDataname") Use the revQueryDatabase function to select records in a database to work on. The SQLQuery may contain one or more placeholders, which are sequential numbers prepended by a colon. The revQueryDatabase function substitutes the corresponding variable name in the variablesList for each of these placeholders. For example, if you have two variables called "valueX" and "valueY", you can use a SQLQuery that includes placeholders as follows: get revQueryDatabase(myID,"SELECT * FROM empStats WHERE id=:1 OR stat_id=:1 OR population=:2","valueX","valueY") The content of the variable valueX is substituted for the ":1" in the SQLQuery (in both places where ":1" appears), and the content of valueY is substituted for ":2". If you specify an arrayName rather than a list of ordinary variables, the revQueryDatabase function substitutes the corresponding element(keyword) of the array for each of the placeholders in the query: get revQueryDatabase(myID,"SELECT :1,:2 FROM empStats WHERE 1",myArray) The content of the element myArray1 is substituted for the ":1" in the SQLQuery (in both places where ":1" appears), and the content of myArray2 is substituted for ":2". To pass binary data in a variable in the variablesList, prepend "*b" to the variable name. The revQueryDatabase function strips the binary marker "*b" and passes it to the database as binary data, rather than text data. To pass binary data in an array element(keyword), prepend "*b" to the element's value. *Tip:* To execute a SQL query that does not return a record set (database cursor)(glossary) (such as INSERT or DELETE), use the revExecuteSQLcommand instead. Since revExecuteSQL does not allocate storage for returned data, it is more efficient than revQueryDatabase for SQL queries where no data is returned. If the query is not successful, the revQueryDatabase function returns an error message. The error message is never an integer, so you can check whether the query was successful by checking whether the return value is an integer or not. The revQueryDatabase function is part of the Database library. To ensure that the function works in a standalone application, you must include this custom library when you create your standalone. In the Inclusions pane of the Standalone Application Settings window, make sure both the "Database" library checkbox and those of the database drivers you are using are checked. Changes: The revQueryDatabase synonym was added in version 2.0. Parameters: *databaseID: The number returned by the revOpenDatabase function when the databasewas opened. *SQLQuery (string): A string in Structured Query Language that contains a SELECT statement.(Do not include a semicolon at the end of the SQLQuery.) *variablesList: The variablesList consists of one or more variable names (or expressionsthat evaluate to variable names), separated by commas. As of version2.9, each variable name can also be the name of an array element, forexample "tInputDatamyKey". *arrayName (array): The name of a single array variable whose keys are sequentialnumbers.]]*Note:* The variable names or arrayName must be enclosed inquotes; otherwise, the variable's value rather than its name is passedto the revQueryDatabase function. * Returns:The revQueryDatabase function returns a record set ID whichdesignates the record set (database cursor)(glossary) selected by theSQLQuery. The record set ID is an integer. See also: revExecuteSQL (command),function (control structure),revQueryIsAtStart (function),Database library (library), Category: database